70' Duster rear end, trans upgrades

I was going to say go with the Dana because my four-speed did in a new eight and three-quarter 489 case within about 20 passes at the dragstrip again that was full Slick's. Then I seen the picture of you're eight and three quarter housing and I was like oh yeah that looks like it will hold LOL.
8 4/4 = 9? Am I missing something here?
I know there's a couple different brackets that attach to the bellhousing side depending on what car that make it line up correctly. I know I was using a used set up and ended up that was the one piece I had to buy to correct the geometry.